1. Field of the Invention
The present invention relates to outdoor lighting controls and, more particularly, to reducing electrical energy usage and increasing the life span and durability of such controls.
2. Description of the Related Art
A conventional photocontrol arrangement employs a photosensor for detecting outdoor ambient light and for converting the detected light into an analog electrical signal. A level detector converts the analog signal into a digital signal having high and low states corresponding to daylight and nighttime conditions, respectively. The digital signal is conducted to an electrical load switching relay which, in turn, switches the load, i.e., an outdoor lighting system, off during daylight, and on during nighttime.
The load relay used in all known photocontrol arrangements have a pair of contacts which are "electrically held", that is the contacts are held apart in an open state as long as the load relay is electrically energized by an electrical current conducted to a coil of the load relay. When this electrical current is discontinued, the load relay is not energized, and the contacts return to the closed state. A reverse arrangement is also possible when the contacts are held closed when the relay is energized.
In either event, the load relay is using electrical energy to hold the contacts together or apart, either all day long during one of the states, or all night long during the other of the states. This is not only wasteful of energy, but also can cause overheating, particularly in small photocontrol enclosures.
Moreover, electrically held relays generally operate over a wide range of input voltages, for example, 105V to 285V and, as a result, a voltage regulator is needed. This regulator also consumes non-negligible power.